The present invention relates to hydrants and more particularly to freeze-resistant in-ground sanitary yard hydrants.
Yard hydrants are installed in water systems to provide water sources remote from buildings. In low temperature climates, such as the mid-west and east coast of the United States, the water lines are buried below the frost line to prevent them from freezing and bursting. Similarly, the lower ends of the hydrants are buried below the frost line to prevent damage to the hydrant arising from freezing. Because the water must reach above ground, the upper part of the hydrants extends up through and above the ground (above the frost line), and is thus subject to the adverse effects of low temperatures.
Typical yard hydrants have a main water supply valve, a dry pipe, a wet pipe and an activation handle. The dry pipe is secured to the main valve housing where the water line is connected below the frost line. The dry pipe then extends up through the ground to a comfortable operating position above ground level. The wet pipe is positioned within the dry pipe and its lower end activates the main valve to turn off and on the water supply. The handle is mounted to the top end of the dry pipe and is linked to the upper end of the wet pipe to raise and lower the wet pipe and thereby control the valve from above ground. The upper end of the wet pipe has a spigot which can connect to a hose or spray out the water directly. To turn off the hydrant, an operator moves the handle to move the wet pipe and close the valve. Any water in the wet pipe will drain out of the hydrant below the frost line, and thereby prevent water from freezing within the hydrant. U.S. Pat. No. 6,178,988 discloses one such hydrant design.
One problem with such hydrants is the presence of the drain to evacuate the water in the hydrant. The drain opening raises two concerns. First, if water is drained from the hydrant it may be necessary to create a drain field so that the water does not accumulate around the hydrant. This makes installation much more labor intensive, time consuming and costly. Also, dispensing water underground may be regulated in certain areas. Second, the drain opening provides an entry point for underground contaminants into the hydrant, which can make the water dispensed by the hydrant less sanitary. This second issue is particularly a problem when valve seals become worn, dislocated or less resilient.
U.S. Pat. No. 6,047,723 discloses a hydrant that collects the water left in the hydrant after it is turned off in a cylinder installed below the frost line. The water collected in the cylinder is purged by a piston back up through the hydrant when the water supply is turned on again. The disclosed hydrant includes a drain opening that is ordinarily isolated from the water collected in the cylinder by one or more o-rings such that normally no water is drained underground. However, should an o-ring fail the water collected water would leak underground. If the o-ring failed while the water supply was on, supply water could be diverted from the hydrant, which could not only flood the area underground surrounding the hydrant but also reduce the water pressure leaving the hydrant above ground.
To avoid these concerns, no-drain hydrants have been devised (see e.g., U.S. Pat. Nos. 3,936,207 and 5,701,925). In such no-drain hydrants, water left in the upper part of the hydrant is collected in a well chamber of the hydrant below the frost line. This chamber is enclosed with no openings (other than for the supply water inlet) that could cause leakage or be an entry point for contamination. Since the chambers are enclosed it is possible for a vacuum to form inside the hydrant which can cause two problems. First, the vacuum can pull water back into the hydrant from a hose or other attachment, which can impact the sanitization of the water and may be prohibited by regulation in certain areas. Second, the vacuum can impede or prevent all of the water left in the hydrant from draining into the well chamber. Water can thus remain above the frost line and freeze, thereby leading to damage or failure of the hydrant.
U.S. Pat. No. 3,926,207 discloses a hydrant having a pair of check valves located in the head of the hydrant (above ground) that will vent the collection chamber to ambient. The check valves are normally open so that the hydrant is vented when off. Water pressure closes the valves when the hydrant is on. One problem with this design is that there is no positive actuation of the valves to ensure they open to vent the hydrant. The check valves in the disclosed hydrant are spring flapper type valves that are biased open. The spring force is overcome by the force of the pressurized water, which when shut off allows the check valves to re-open. Such a valve arrangement is prone to failure, particularly when the air temperatures are below freezing, in which case water on and around the check valves can freeze causing ice to build up on or around the valves, which can disrupt the seal or hold them closed. The result of this is that the water either sprays through the check valves or the check valves fail to vent the collection chamber causing the aforesaid back siphon problems.